Hi in this video, we're gonna be talking about developmental patterning genes. So the very first, let me come back there with the very first stage of development is really just determining which part of the organism is going to become the front, the back, the top and the bottom. And so let's learn the names like the official scientific names of front, back, top and bottom. So uh there's an interior. This is going to be the front. Also you think of it as a head. You have posterior which is the back, you have dorsal which is the top and ventral is the bottom. And I have a picture of this. And then there are going to be many different genes that control the positioning, also called the patterning of these locations. So there's two classes we have the maternal effects jeans. And these are actually maternal genes. So they come from the egg themselves. So for the mother, not the organism that's developing the mother that's housing that organism that's developing. And so these are found within the egg. And these are the very first developmental genes that happened. So before the organism starts doing anything with its own genes, the mom's genes actually impact development. It's the earliest portion of development. Then after those maternal genes are activated, they're doing their work. They generally activate the second set. And these are the psychotic genes. So this is that organism that's development. So the embryo's genes control the later stages of development of that early development. So here we have a fish. We have don't worry about all these other things that are on here, you don't need to know this, know the anterior posterior dorsal and ventral, anything in a circle. No, the rest of it, you can just scribble out. And so those are the different locations of the fish and most organisms. So now let's talk about the genes. So we have segmentation genes are the first genes that come into play and these control specific segments of the organism. So that's gonna be what's going to be the head and insects, that's what's gonna be the an tanna, what's going to be the thorax or the abdomen. These types of uh segments even before they become thorax and Tana. That actually happens later. But it's just sort of segmenting and saying, okay, this is gonna be the anterior and this is going to be posterior dorsal ventral side and there's gonna be some segments in there. So even before we get too specific things like abdomen. So like I said before, the very first genes that come into play are the maternal effect genes. And so the two that are really important are going to be big coid and nano's. So we have a cell, right, this is this is our cell, this is the cell we start off with um and what forms the anterior and posterior in is actually concentrations of these two genes. So we'll say that by coid is going to be read And the higher concentration that there is. So over here with a lot of it over here is gonna be the anterior region. Whereas nano's is going to be opposite. The higher concentration that it has. So over here is going to end up being the posterior side of the organism. So this is the very first thing that controls the position of the organism. It happens in the single cell and it happens through maternal genes. So these are the moms jeans, not the zygote genes. Once we have Bitcoin and nano's express, these genes go on to express the second set of genes which are gap jeans. And these are psychotic genes. So these are the first genes of the actual organism that's developing and this divides the embryo into body segments. And I've mentioned just a couple of ones that you might read about in your textbook, these are the gap jeans. The gap jeans didn't go on to activate the pair. Roll jeans again, psychotic jeans. And these results in pair of segments. Then we have a segment polarity genes and these results in the anterior posterior of each segment. So here we developed that for the whole organism. But when we start getting the segments that start coming into the organism, each one needs to say this is anterior and besides posterior and the segment polarity genes do that. And so I mentioned this before but I want to make sure you understand is that the concentration of each gene activates the next step. So the maternal genes activate gap when gap is present. That concentration will activate payroll when payroll is present. That concentration will activate segment. So it's this cascade of these different genes, the maternal spurs. Then gap payroll segment polarity and each one activates the previous one. So like I said here by coin is gonna activate, Gap. Gap activates payroll and payroll activate segment clarity. So this is the image that you're most likely going to see in your book. So we have anterior posterior of this of the cell or this early embryo. Um This is actually an early embryo. Then we have earlier and later in development. So earlier we start out with bike oid is actually the different colors than I did before and nano's and that controls posterior and anterior. Then these go on to activate the gap jeans which are here in purple and green. And these start saying okay well here's one segment. Here's a second segment, Here's the third segment. And these segments are going to be important for later development. Then we start having the pair rolls even skips a payroll payroll gap, maternal. And these start dividing into even more segments. Right? You can see all these different segments here and then we have finally the last one an example of this is wing list. This is the segment polarity and this starts saying okay well this segment this anterior that's posterior this segment anterior posterior and for so on and so forth for all the different segments. And obvious basically these segments are super important. The segments get messed up. The organism development is just completely just ruined essentially. It's so screwed up. Doesn't live. Um It's so screwed up. So these early genes in their concentration gradients are super important. Um And notice they are gradients right? You can see that at least for the maternal effect it's fading and saying that there's a really high concentration of nano's over here and a really faint concentration or low concentration of nano's here and that actually impacts you know where the gap jeans for the next step are expressed. So concentration gradients are super important in these early stages to make sure that all the segment genes are expressed in the right location and these segments get formed correctly after the segment genes do their job. There's a second pair of jeans that come in because of the homoerotic genes. Or the hawks genes you'll most likely see them as hawks. And to underline that hawks and these control actual organ development or even further segment development. So things like the antenna, the abdomen, the legs, the thorax. This is what the hawks genes control and they control in the previously defined segments. And so um these are names such because they have this thing called a home box. It's around 180 base pairs. Remember their genes? Right? So they have base pairs because their D. N. A. And these genes contain a home a box of 100 and 80 base pairs which has a homo domain in the protein forms I remember they become proteins and these form a homo domain that actually ends up binding D. N. A. Through a helix turn helix motif. Not super important to understand the motif but just throwing it in there in case you care. So these genes contain a little segment of DNA. That when it's turned into a protein into the into the hawks proteins they actually will bind D. N. A. And so if they bind D. N. A. What does that suggest their function is what other things bind D. N. A. That we've talked about previously. Right? So these proteins are most likely acting as transcription factors in some way they're activating or inhibiting gene expression because they combined two D. N. A. And main mainly things that bind to D. N. A. Affect transcription. So think of these as transcription factors activating or repressing all these different clusters of genes now in fruit flies which is what we're mainly going to focus on in development. There are two clusters of hawks genes, their name the antenna PDE to and the by thorax. The antenna pd A. Has five genes in it and these control the head and thorax development. Then we have the by thorax which has three genes that controls the posterior portion of the thorax and the abdominal. And so when we look at the fruit fly here, we have our antenna pd a jeans one. Let me let me disappear here. We have our 112345. We have our by thorax genes 123. And you can see that if you match the colors with the a respective place on the fruit fly, you can see that these genes actually control every single segment of this organism and how it's going to develop. And so these are super, super important. Um jeans hawks genes that active transcription factors that activate genes that will, you know, make the antenna or make the mouthpiece or make the front legs or make the thorax or all these different regions that will be made. Now hawk scenes are extremely well conserved. They are found in pretty much in all organisms, but some animals have more hawks gene clusters than fruit flies. Fruit flies have these two Mice have four. and this the more hawks genes you have, the more that likely that it's going to be that some of them have duplicated functions. So in fruit flies, if any single one of these genes get messed up, that's going to mess up the actual organism. So if the front leg thing is mutated, that means this thing is this fly is not going to have front legs or anything resembling useful or functional front legs and that's obviously going to be very harmful to the organism itself. But if you have more hawks genes, it's more likely that some of these are going to overlap in their functions. So you may have two genes that control different portions of the front leg. So if one of them gets messed up, there's still a chance that you will be able to have functional front legs even if they look a little wonky. Um And so the more hawks genes is obviously better, but generally they all have the same function. They divide the organism into these segments that then activate these genes. That will develop into these segments, develop those cells into these segments so super, super, super important and development. So with that let's now turn the page.
Plant HOX genes
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Okay, so now let's talk about plant development and plant genes. So, so far we've all talked about animals, but plants actually contain their own set of homoerotic genes, or hawks genes. And so in arabidopsis, which is typically the model organism used for um, used to study plants. There are three classes of hawks genes. Um very easily labeled Class A. B. And C. Now in the plant class A. Forms the sea peoples. If you have a segment that's expressing A. And B, that's gonna be the pedals, you have a set of region expressing B. And C. That's gonna be the statement. And if you have a thing that's expressing only see that's going to be the carpools. Now, if you're like me and aren't really quite up today on your plant anatomy, let's let's refresh this. So, here's the plan. Obviously we know the pedals, right? There's lots of things here. Don't you don't need to know this. We're not in a plant's class. Right? But we, the things that we're interested in, we're interested in see people's pedals, statements and carpools. So here's the statement. So this is this thing here is statement, right? We have pedals which we um, did here, we have the car pulls, which is actually going to be, uh, this thing here, this green thing here is the carpal and the sea people is actually these little uh kind of baby leaves down here, the people. So these are the four things we're worried about. So if we look over here at this plant, you can see the classes are down here. So A is blue bee is yellow and see is red. So class A forms the sea people. Remember these little baby leaves down here. So if we look at where only A. Is expressed, that's that's the sea peoples. If we look at where A. And B. Are expressed. So anything with blue and yellow on it, that's gonna be the pedals, which are things we're most familiar with. If we look at B and C. So yellow and red, that's gonna be the stamen. Remember the stamen? Is this thing here? So that's there and then finally class C. Is burns the carpal which is only red and that is here carpal stay men pedal and see balls just in case you're not familiar with the plant development. Hopefully that helps. But this is plant development. They use these hawks genes as well. Um, they're just labeled Class A, B. And C. Instead of the ones that are labeled that way in fruit flies. So with that let's now move on.
Which genes are the first genes that control patterning of the offspring during early development?
Maternal effect genes
Areas with higher bicoid expression will develop into which body pattern?
Activation of the segmentation genes occurs in which of the following orders?
Maternal effect → gap → segment polarity → pair rule
Gap → maternal effect → pair rule → segment polarity
Maternal effect → gap → pair rule → segment polarity
Segment polarity → pair rule → gap → maternal effect
Which of the following HOX clusters are responsible for forming the abdominal in Drosophila development?
In Arabidopsis, which class of HOX genes are responsible for forming the plant carpels?